Modulation of prostaglandin metabolism is at the center of current anti-inflammatory therapies. NSAIDs and COX-2 inhibitors block the activity of cyclooxygenases and their ability to convert arachidonic acid into prostaglandin H2 (PGH2). PGH2 can be subsequently metabolized by terminal prostaglandin synthases to the corresponding biologically active PGs, namely, PGI2, thromboxane (Tx) A2, PGD2, PGF2α, and PGE2. A combination of pharmacological, genetic and neutralizing antibody approaches demonstrates the importance of PGE2 in inflammation. The conversion of PGH2 to PGE2 by prostaglandin E synthases (PGES) may therefore represent a pivotal step in the propagation of inflammatory stimuli.
Microsomal prostaglandin E synthase-1 (mPGES-1) is an inducible PGES after exposure to pro-inflammatory stimuli. mPGES-1 is induced in the periphery and in the CNS by inflammation and represents therefore a target for acute and chronic inflammatory disorders.
PGE2 is a major prostanoid driving inflammatory processes. The Prostanoid is produced from arachidonic acid liberated by Phospholipases (PLAs). Arachidonic acid is tranformed by the action of Prostaglandin H Synthase (PGH Synthase, cycloxygenase) into PGH2 which is a substrate for mPGES-1, that is the terminal enzyme transforming PGH2 to the pro-inflammatory PGE2.
NSAIDs reduce PGE2 by inhibiting cyclooxygenase, but at the same time reducing other prostanoids, giving side effects such as ulcerations in the GI tract. mPGES-1 inhibition gives a similar effect on PGE2 production without affecteing the formation of other prostanoids, and hence a more favourable profile.
By blocking the formation of PGE2 in animal models of inflammatory pain a reduced inflammation, pain and fever response has been demonstrated (see e.g. Kojima et. al, The Journal of Immunology 2008, 180, 8361-6, Xu et. al., The Journal of Pharmacology and Experimental Therapeutics 2008, 326, 754-63).
In abdominal aortic aneurism, inflammation leads to connective tissue degradation and smooth muscle apoptosis ultimately leading to aortic dilation and rupture. In animals lacking mPGES-1 a slower disease progression and disease severity has been demonstrated (see e.g. Wang et. al. Circulation, 2008, 117, 1302-1309).
Several lines of evidence indicate that PGE2 is involved in malignant growth. PGE2 facilitates tumour progression by stimulation of cellular proliferation and angiogenesis and by modulation of immunosupression. In support of a role for PGE2 in carcinogenesis genetic deletion of mPGES-1 in mice supress the intestinal tumourogenesis (Nakanishi et. al. Cancer Research 2008, 68(9), 3251-9). In man, mPGES-1 is also upregulated in cancers such as clorectal cancer (see e.g. Schröder Journal of Lipid Research 2006, 47, 1071-80).
Myositis is chronic muscle disorder characterized by muscle weakness and fatigue. Proinflammatory cytokines and prostanoids have been implicated in the development of myositis. In skeletal muscle tissue from patients suffering from myositis an increase in cyclooxygenases and mPGES-1 has been demonstrated, implicating mPGES-1 as a target for treating this condition (see e.g. Korotkova Annals of the Rheumatic Diseases 2008, 67, 1596-1602).
In atherosclerosis inflammation of the vasculature leads to atheroma formation that eventually may progress into infarction. In patients with carotid atherosclerosis an increase in mPGES-1 in plauqe regions have been found (Gómez-Hernández Atherosclerosis 2006, 187, 139-49). In an animal model of atherosclerosis, mice lacking the mPGES-1 receptor was found to show a retarded atherogenesis and a concommitant reduction in macrophage—derived foam cells together with an increase in vascular smooth muscle cells (see e.g. Wang Proceedings of National Academy of Sciences 2006, 103(39), 14507-12).
The present invention is directed to novel compounds that are selective inhibitors of the microsomal prostaglandin E synthase-1 enzyme and would therefore be useful for the treatment of pain and inflammation in a variety of diseases or conditions.